Coloring of acrylonitrile polymer filaments



United States Patent 3,242,243 COLORING OF ACRYLUNITRILE POLYMER FILAMENTS John P. Knudsen, Raleigh, N.C., assignor, by mesne assignments, to Monsanto Company, a corporation of Delaware No Drawing. Filed Apr. 4, 1962, Ser. No. 184,945 11 Claims. (Cl. 2654-48) This invention relates to a process for coloring acrylonitrile polymer filaments and fibers, and more particularly it relates to a method for integrally coloring such filaments and fibers while wet spinning same.

It is well known that polyacrylonitrile and copolymers of acrylonitrile and other monoolefinic polymerizable monomers are excellent fiber-forming materials. The polyacrylonitrile and copolymers of more than 80% of acrylonitrile and up to 20% of other polymerizable monomers produce fibers with superior textile properties, desirable elongation, and excellent stability under a wide range of physical and chemical conditions. However, these polymers are subject to certain inherent disabilities which restrict their utility in the fabrication of general purpose fibers. For example, the fibers are not readily susceptible to dyeing by simple, straight-forward and rapid dyeing processes common with most natural fibers.

The dye-receptivity of acrylonitrile polymer filaments and fibers has been greatly improved by utilizing as the comonomer certain basic compounds, particularly heterocyclic compounds containing a tertiary nitrogen in the ring and substituted with .a polymerizable monoolefinic group. Still further improvements in dye-receptivity and other properties of acrylonitrile polymer filaments and fibers have been efiected by blending polymers or copolymers of acrylonitrile containing at least 80% of acrylonitrile in polymeric form with a second copolymer containing :at least 30% of a basic monomer, which is preferably a heterocyclic compound containing .a tertiary nitrogen atom in the ring and a polymerizable monoolefinic group substituted thereon. Although incorporation of the dye-receptive monomers has enabled the production of filaments and fibers having greatly improved dyereceptivity, with those dyestuffs relatively substantive to the particular dye-receptive monomers used, it has not enlarged the classes of dyestufis useful for dyeing such filaments and fibers, it has not resulted in greatly shortening the normal dye bath cycles in dyeing such filaments and fibers, nor have the dyeings realized with filaments and fibers from such modified polymers frequently been as fast as has been desired to washing and exposure to light. Consequently there has long been evidenced a need for a rapid, efficient and effective means of coloring acrylonitrile polymer filaments and fibers with all, or essentially all, of the available classes of dyestuffs in much shorter times than has been possible with the prior art dyeing procedures and to good shades of acceptable wash and light fastness.

The normal dyeing processes of the prior art are exemplified in those in which completely formed, dried and finished filaments and staple fiber yarns in skein form or, more generally, in the form of fabrics, are dyed in dye-baths over extended periods of time of 1 to 6 or more hours at temperatures approaching or exceeding the boil and at times under superatmospheric pressure. It is readily apparent that a coloration process which can give shades of equal color value and equal or superior fastness in a matter of seconds results in tremendous economies in manpower, equipment and time required for the production of colored filaments, fibers and fabrics derived therefrom. The present invention represents a process in which such results can be achieved in periods as short as /2 to 10 seconds.

Improvements have been desired in the coloring of acrylonitrile polymer filaments and fibers that will enlarge the scope of available dyestuffs which can be employed. Many of the classes of excellent dyes substantive to natural fibers or other types of artificial and synthetic fibers have not been suitable for use in dyeing acrylonitrile polymer filaments and fibers because those dyestuifs have too low or practically no ailinity for the dye sites available in the acrylonitrile polymer filaments and fibers. This problem exists even in those of such fibers modified specifically to include dye sites for certain types of dyes such as those polymeric fibers containing polymer or copolymers of N-heterocyclic monoolefinic monomers. Dyes which have not been employed on acrylonitrile polymer fibers to any extent include sulfur dyes and va-t dyes. On polyacrylonitrile or acrylonitrile copolymers which do not contain an acid dye-receptor, such as the tertiary N-heterocyclic monoolefinic monomer dyes from the classes of acid dyes, direct dyes, acid metallized dyes, and neutral metallized dyes have not normally been employe because of the slight substantivity of such dyes for the dye sites of the polymers. This low or sparing substantivity or afiinity for the polymers composing the fibers and filaments results in weak or essentially no dyeing because too great concentrations of the dyes are required for practical application or there is simply so little affinity that no color build-up results irrespective of the concentration of dyestutf employed in the dye-bath. Thus, there has long been desired a coloration process for acrylonitrile polymer filaments and fibers which could employ these excellent classes of dyes affording a very extended range of colors and shades use of which has heretofore not been either possible or feasible. None of the dyeing processes of prior art have enabled the use of many of these dyes as practical dyes employed in the commercial dyeing of acrylonitrile polymer filaments and fibers and, hence, .a great number have been unavailable to the dyer for this purpose.

Methods for the coloring of acrylonitrile polymer filaments and fibers disclosed in the prior art have been directed towards solutions to one or more of the problems, but they have not been very successful in that regard. One approach to these problems by the prior art has been to modify the usual dyeing processes with only the well-known classes of dyestuffs available by the use of various types of dyeing assistants or pretreating agents for increasing the dye uptake of the acrylonitrile filaments and fibers. Superatmospheric pressures and temperatures above the boil have been found necessary with many dyeing processes to achieve good color values. The prior art methods including the use of mineral acid and other pretreating agents and the use of dye carriers such as parabenzyl phenol have shortened the prior time of dyeing only to a very limited degree, and have not resulted in the use of any other types and classes of dyestuffs than those already available. Also, they have usually resulted in decreased wash and light fastness in the resulting dyeings, since, although dyed t deeper shades, the dye has been more easily removed in wash tests with soap and dilute alkali solutions and a break from true shade on exposure to natural sunlight or Fadometer testing has frequently occurred sooner.

The attempts to secure very wash and light fast shades in acrylonitrile polymer filaments and fibers by the prior art have included mass pigmenting or solution dyeing processes in which inorganic or very stable organic pigments were dispersed in the spinning solutions or dopes of acrylonitrile polymers in a solvent therefor and those dopes then subjected to dry or wet spinning processes. Although these processes resulted in colored acrylonitrile polymer filaments with very high wash and light fastness the processes have disadvantages from the standpoint of efficiency, cost, and commercial attractiveness. They involve additional cost for specially prepared pigments or coloring materials, high labor costs and are quite inefficient in that all the dope lines from the area at which the pigment is introduced into the dope, line filters, spinnerets, coagulating baths, etc. are contaminated with the given pigment being spun and require replacement or long term shut-down for cleaning before it is possible to change to a different color or shade. Because of the difficulty in spinning these filaments and fibers the range of colors and shades available is necessarily quite limited. Such processes employ few if any of the existing classes of dyestuffs as contrasted to pigments.

One approach taken by the prior art has involved the dyeing of filaments or fibers of acrylonitrile polymer when in the gel or aquagel state before the final degree of crystallinity and orientation of the filament is developed by stretching, collapse and drying of the fiber to its final dry diameter. Many disadvantages reside in this prior art process and it has never been commercially employed as far as is presently known. The disadvantages involve the length of time required for the dyestuff to be absorbed by the filament in its aquagel state which, although much shorter than that of the finished and dried fiber subjected to a boiling dye bath, is nevertheless quite lengthy compared to the period of coagulation, washing and processing of the fiber normally done in dry and wet spinning processes. Furthermore, it is usually necessary to include some dyeing assistant such as a surfactant, humectant, or other assistant to aid in the even dyeing of the filaments and, because of the presence of such assistants, the fastness to washing and, to some extent; light is not as high as might be expected or desired. For these reasons this prior art process has not been utilized commercially nor found to answer the problems in coloring acrylonitrile polymer filaments and fibers rapidly, efficiently and to acceptable fastness to Washing and light.

Accordingly, an object of this invention is to provide a process for coloring acrylonitrile polymer filaments and fibers which is extremely rapid and efficient. Another object of this invention is a process which permits the use of many classes of dyestuffs previously unavailable for the dyeing of acrylonitrile polymer filaments and fibers. A still further object of this invention is a process for coloring acrylonitrile polymer filaments and fibers to shades demonstrating high fastness to washing and exposure to light. A still further object of this invention is the provision of a process for coloring acrylonitrile polymer filaments and fibers which is highly etficient and economical, requires a low expenditure of labor and equipment, and can be carried out in existing equipment for the production of said filaments and fibers.

These and other objects of the instant invention are accomplished by a process for coloring acrylonitrile polymer filaments and fibers which consists in extruding a solution of an acrylonitrile polymer in a solvent therefor into a coagulation bath consisting of a precipitant for the acrylonitrile polymer and an amount of a dyestuff soluble in the coagulation bath sufiicient to color the resulting coagulating filament or fiber. Depending only upon the requirement that any dyestuff so employed must be either completely or at least sparingly soluble ell) in the coagulation bath, this process is otherwise unlimited in the classes and types of dyestuffs which may be used. Generally the amount of such dyestuffs necessary to impart color to the resulting coagulated filaments or fibers depends upon several factors including the identity of the polymers being extruded, the substantivity of the specific dyestuff to the specific polymer employed, and in the depth of the color desired. Generally the amount of such dyestuffs will range from about 0.1% to about 10% based on the weight of the coagulation bath. The most preferred amounts of such dyestuffs are from 0.2% to 3% based on the weight of the coagulation bath.

The wet spinning of acrylonitrile polymer filaments and fibers broadly comprises extruding a solution of the polymer in a solvent therefor into a liquid coagulating bath containing a precipitant or non-solvent for the polymer which is likewise a solvent for, or miscible with, the solvent in the extruded polymer solution, whereby the same is removed from the coagulated or precipitated acrylonitrile polymer filament. There have been developed many systems of solvent and polymer extrusion solutions or dopes and there have been many precipitants disclosed for forming coagulation baths of varied composition. It was unexpectedly found that all such known extrusion and coagulation systems are susceptible to the present process.

Among the wet spinning systems known for the production of acrylonitrile polymer filaments and fibers the earliest used was a spinning solution or dope composed of a solution of the acrylonitrile polymer in aqueous solutions of certain inorganic salts, such as calcium chloride, zinc chloride, sodium thiocyanate, etc. In this system the dopes were extruded into much more dilute baths of aqueous solutions of the same or other inorganic salts, frequently at a much lower temperature than that at which the spinning solution was maintained and extruded from the spinneret. The process of the present invention functions in such wet spinning systems excellently to give filaments and fibers of good color value and wash and light fastness, dependent only on the requirement that the dyestuff employed must be one which is soluble in the dilute aqueous solution of inorganic salts employed as the coagulating bath at the temperature at which said bath is maintained. All of the classes of water-soluble dyes such as acid, direct, acid metallized, neutral premetallized, basic or cationic dyes, sulfur dyes and the leuco ester forms of vat dyestuffs as well as those sparingly water-soluble dyes of the general class of dispersed dyestuffs are suitable and can be employed with spinning systems employing aqueous solutions of metallic salts.

Other successful wet spinning processes employ organic solvents for the acrylonitrile polymers to be extruded, such as dimethylformamide, dimethylacetamide, ethylene carbonate, gamma-butyrolacetone, tetramethylene sulphone, dimethyl sulfoxide, etc., and extrude these spinning dopes into coagulation baths composed of the same or other organic solvents and water at varying degrees of dilution. The process of the instant invention is suitable with all of these organic solvent wet spinning processes including those in which the coagulation bath ranges from a concentration of as low as 20 percent of the organic solvent to as high as 85 percent or more of said solvent at any of the temperatures chosen to operate for various physical properties desired. In these processes all of the same water-soluble types of dyestuffs detailed above as well as dispersed dyes can be successfully employed. The dispersed dyes are soluble to a much greater degree in the organic solvent baths than in water alone.

Variations of the coagulation baths and precipitants employed together with organic solvent spinning solutions or dopes are also known and the process of the present invention can be employed with these aswell. Such processes include those in which an organic solvent spinning dope is extruded into an aliphatic hydrocarbon precipitant With or without addition of the same organic solvent, such as aliphatic kerosene containing varying percentages of dimethyl formamide into which there is extruded a spinning solution of an acrylic polymer in dimethyl formamide. The same is true of those spinning systems which employ as the precipitant glycerols, glycols, such as ethylene glycol, or polymeric glycols, such as polyethylene glycols of molecular weights from 200 to 6000, with or without the addition of some of the same organic solvent comprising the spinning dope. With these systems all classes of dyestuffs which are soluble in the coagulating bath can be employed. The classes of dyes useful in coagulation baths of aliphatic hydrocarbons include those classed as oil-soluble" dyes and dispersed dyes. With coagulating baths using precipitants such as glycerol, glycols, or polymeric glycols all of the dyes useful in baths of organic solvents and water are generally useful, including basic, direct, acid, acid metallized, neutral premetallized, sulfur, leuco esters of vat dyes and dispersed dyes. Thus, it is seen that with all the prior art wet spinning processes known the process of the present invention can be utilized for coloring the acrylonitrile polymer filament and fiber products.

With those of the above spinning processes in which the coagulation process involves an inward diffusion of the coagulating bath or precipitant and a concomitant outward diffusion of the polymer solvent, whether it be an aqueous solution of metallic salts or an organic solvent therefor, the mechanism of coloring the fiber performs excellently. By this, it is meant that rather than ring dyeing there is obtained a complete penetration of dyestufi in a matter of fractions or a very few seconds of immersion in the coagulating bath which, upon further orientation of the polymer filament, and final drying thereof, results in a coloration which is generally more permanent, more light and wash fast and with better color value than those realized by conventional dyeing procedures. The colorations obtained are better in these respects than those in which a separate dye bath immediately following the coagulation bath is employed, as has been proposed in the prior art, as will be more fully illustrated in the examples which follow. These results are believed to be due to the infusion into the just-precipitating polymer mass of the dyes along with the coagulating solution which is infusing into the polymer matrix and displacing the solvent solution from which the filaments were spun. Those already formed and precipitated filaments in the aquagel state are not so readily infused with dyestuff from a separate bath as is more fully shown below.

In those of the above systems which do not employ aqueous coagulating baths the same general mechanism takes place with the present invention. That is, in those baths employing aliphatic hydrocarbons, glycerol, ethylene glycol or other non-aqueous but readily diffusible precipitants the same infusion and displacement mechanism takes place and the infusion of the dyestuffs takes place concurrently therewith. In those systems in which the precipitant is a highly polymeric material such as polyethylene glycol there is less infusion into the matrix of the forming polymer filament but there is sufficient of dyestuffto result in permanent and good coloration of the resulting filaments and fibers.

The acrylonitrile polymers from which are produced the filaments and fibers with which the present process for coloration is suitable include all predominantly acrylonitrile polymers. The present invention is applicable to all acrylonitrile poly-mer filaments and fibers produced from polymers, including copolymers and interpolymers, containing 80 or more percent by weight of acrylonitrile in polymerized form and blendsof such polymers with relatively small amounts of blending polymers. In addition to polyacrylonitrile the copolymers and interpolymers can be polymers of or more percent of acrylonitrile and minor proportions of other monoolefinic monomers copolymerizable therewith. Among the monoolefinic monomers useful for copolymerizatiori with acrylonitrile are vinyl acetate and other vinyl esters of monocarboxylic acids having up to four carbon atoms, methyl acrylate and other alkyl acrylates having up to four carbon atoms in the alkyl radical, methyl methacrylate and other alkyl methacrylates havingvup to four carbon atoms in the alkyl radical, acrylic, alpha-chloroacrylic and methacrylic acids, vinyl chloroacetate and other vinyl esters of halogen substituted monocarboxylic acids, dialkyl fumarates, maleates and crotonates having up ot four carbon atoms in the alkyl radicals, styrene, alpha-methylstyrene, and other vinyl or alkenyl-substituted aromatic hydrocarbons, vinyl chloride, vinylidene chloride and other vinyl and vinylidene halides, methacrylonitrile, methyl vinyl ketone, N-vinyl carbazole, vinyl furane, and those tertiary N-heterocyclic compounds substituted with a polymerizable monoolefinic group, such as vinyl or other alkenyl, which may be employed for increasing the affinity of certain dyestuffs, such as vinyl pyridines and alkyl-substituted vinyl pyridines, vinyl or alkenyl lactams such as vinyl pyrrolidone, vinyl imidazole and alkyl-substituted vinyl imidazoles, vinyl quinolines, vinyl pyrazines, vinyl oxazoles, and vinyl benzimidazoles. The blended compositions can be blends of 80 to 98% by weight polyacrylonitrile, and any of the above copolymers and interpolymers with minor proportions, 2 to 20% by weight, of one or more blending polymers which are themselves hornopolyrners or interpolymers containing at least 30% of a readily dyeable basic component such as the vinyl or alkenyl-substituted tertiary-N-heterocyclic compounds above and up to 70% of any of the above other monolefinic monomers copolymerizable therewith and acrylonitrile.

The following examples in which parts, proportions, and percentages are by weight unless otherwise indicated, further illustrate the application of the principles of this invention.

In Examples I through VII below the same general extrusion and coloring procedure was employed. This procedure consisted in extruding a polymer dope consisting of approximately 25% polymer solids of an acrylonitrile copolymer of 94% acrylonitrile and 6% vinyl acetate by weight in polymerized form in dimethylacetamide containing 2% by weight of acetic acid into coagulation baths composed of 55% dimethylacetamide, 45% water, 1.5% of the total bath weight of the particular dyestuif, and sufficient ammonium acetate to produce an initial pH in the coagulation bath of about 5.4. The extruded filaments were conducted through the coagulation bath for a distance of 12 inches at a rate of about 21.5 feet per minute and were thereafter conducted out of the bath and washed with water at 95 C. over rotating rolls prior to stretching for orientation in a trough or cascade of about 12 inches containing flowing water at from 95 to 99 C. In the cascade the filaments were subjected to a stretch of 4.38 times, a standard acrylic polymer filament finish to a total amount of approximately 1% on basis of fiber weight was applied thereto by dipping into a bath of finish dispersion, were dried by passing several times around heated drying rolls and thereafter collected on a wind-up bobbin. The resulting samples of yarn were knitted into circular knit tubing and submitted for determinations of light and wash fastness. The results of these determinations are reported in the examples set out below.

Example I The above outlined wet spinning process was employed to spin acrylonitrile polymer filaments of a co polymer of about 94% acrylonitrile and 6% vinyl acetate colored by a direct dye, Belamine Fast Red 3 BL (Direct Red A3; C.I. 29225). The pickup of this dyestutf realized in the 2.8 seconds residence in the coagulation bath was relatively good to produce a light to medium maroon shade. The resulting knitted yarns when tested for light and wash fastness demonstrated a Fadometer light fastness to first noticeable break in shade of 120 sunlight fading hours and a very good wash fastness when tested by AATCC wash test No. 4 at 182 F. showing only a class 4 staining, which is a barely perceptible staining of attached multifiber strips of other classes of fibers on which the dyestufl? might bleed. The knitted samples also demonstrated very good fastness to both acid and alkaline perspiration tests, showing no staining of an attache-d multifiber strip during these tests.

Example II Employing the same wet spinning procedure as outlined above the same filaments of the same polymer composition were colored with a dispersed dye, Amacel Violet Blue FSI (Dispersed Blue 19; C.I. 61110), in which the dye pick-up in the coagulation bath was good to produce a very deep dark blue shade. The knitted samples of the resulting yarn demonstrated Fadometer light fastness of 80 sunlight fading hours to first break and acceptable wash fastness in AATCC wash test No. 3 at 160 F., i.e., a shade change reading of 3, a noticeable change, and a staining rating of .3 on the attached multifiber strip. In wash test No. 2 at 120 F. there was no staining of the attached strip. This example demonstrates that light and wash fastness results at least equilavent to those obtained by normal dyeing methods are realized by the process of this invention in a time of approximately 2.8 seconds in the coagulation bath.

Example III The same wet spinning procedure as set out above 'was employed to produce filaments of the same acrylonitrile copolymer as above colored with a neutral metallized dye, Cibalan Blue BL (Acid Blue 168). The filaments showed good dye pick-up demonstrating a good navy blue shade. The resulting knitted filaments when tested for fasteness demonstrated a light fasteness of 80 sunlight fading hours and an excellent wash fastness when tested by AATCC wash test No. 4 at 180 F. showing a very slight shade change of a rating of 4 and no staining whatever of the attached multifiber strip.

Example IV A wet spinning conducted in the same manner as above with the same acrylonitrile copolymer employing another neutral metallized dye, Capracyl Red B (Acid Red 182) was conducted. In the same length of immersion in the bath the coagulating fiber showed fair to good dye pick-up and produced a light to medium maroon shade. The resulting fibers demonstrated excellent light fastness of greater than 320 sunlight fading hours to first break and good wash fastness in AATCC wash test No. 2 at 120 F. with a slight change rating of three and barely noticeable staining with a rating of four. In both Example III and this one there was no staining at all on the AATCC acid and alkaline perspiration tests. Examples III and IV above clearly demonstrate the superior light fastness realized with the neutral metallized dyes when applied to a class of polymers to which such dyes are not normally substantive and with which these dyes are not normally employed in ordinary commercial dyeing processes.

Example V The same wet spinning procedure as outlined above was employed with the same acrylonitrile copolymer colored by a sulfur dye, So-Dye-Sul Liquid Black 4GCF (Sulfur Black 1; C. I. 53185). The pick-up of this dye in the same period of 2.8 seconds resulted in a good dark grey shade. The finished filaments tested as a knitted sample demonstrated a light fastness of approximately sunlight fading hours before a break and an excellent wash fastness When tested by AATCC wash test No. 4 at 180 F. showing a slight shade change of a rating of 4 and no staining whatsoever of an attached multifiber strip. This example demonstrates the utility in the present process of another class of dyestuffs, the sulfur dyes, which cannot normally be employed by the prior known processes for dyeing this type of acrylonitrile copolymer because of very low substantivity thereto.

Example VI The same procedure was followed in conducting a wet spinning of the same acrylonitrile copolymer colored by a basic dye, Sevron Blue B (Basic Blue 21). In the 2.8 seconds immersion in the coagulation bath the coagulating filaments showed good dye pick-up producing a very good medium blue shade. The knitted samples of resulting filaments when tested for light fastness demonstrated an excellent-light fastness of sunlight fading hours prior to any noticeable break in shade and an excellent wash fastness when subjected to AATCC wash test No. 4 at 180 F. with a moderate shade change of rating 3 and .no staining whatsoever of the attached strip. This example demonstrates that with classes of dyes which are known to be substantive to this type copolymer results fully equivalent to those of dyeing processes requiring one to three hours are realized in as little as 2.8 seconds by the process of this invention.

Example VII The same wet spinning procedure outlined above was employed to prepare filaments from the same acrylonitrile copolymer colored by a direct dye, Fastusol Blue LFFR (Direct Blue 67; C.I. 27925). In the 2.8 seconds of residence in the coagulation bath the filaments showed good dye pick-up to produce a food medium blue color. The resulting filaments knitted into test samples demonstrated surprisingly excellent light fastness of more than 320 sunlight fading hours prior to any break in shade and excellent wash fastness when subjected to AATCC wash test No.3 at F. showing no shade change and no staining of an attached multifiber strip. This example likewise demonstrates that with another class of dyes not normally employed for dyeing this type of acrylonitrile copolymer surprisingly excellent results in light fastness and wash fastness are obtained by the process of the present invention.

In Examples VIII and IX, essentially the same wet spinning procedure as outlined above was employed but in each case a comparative sample was spun in which the coagulation bath contained no dye and a second bath of the same approximate composition of precipitant and solvent, i.e., 45% water and 55% dimethylacetamide, but containing 1.5% dyestuff based on the total weight of the bath was positoned immediately after the exit of the filaments from the coagulation bath. The filaments in aquagel state were immersed in the second bath to the same 12 inches of immersion as in the coagulation bath just preceeding it. The remainder of the spinning was conducted in the same manner, i.e., washing with hot water, orienting in a cascade of countercurrent flow of boiling water, applying finish and drying. These examples will contrast the amount of dyestuff which can be applied to the forming filaments as compared to those already formed filaments in the aquagel state.

Example VIII (a) The same wet spinning procedure as outlined above was employed to color an acrylonitrile polymer blend composed of 88% copolymer of approximately 94% acrylonitrile and 6% vinyl acetate with 12% by weight of a copolymer of approximately 50% acrylonitrile and 50% methyl vinyl pyridine. And 18% solids solution in dimethylacetamide containing 2% by weight of acetic acid was prepared, and this dope was spun into a coagulation bath containing 1.5% of an acid dye, Anthraquinone Blue SWF (Acid Blue 26; C1. 6205). In this spinning the coagulating filaments showed excellent pick-up of the dyestuff to a deep royal blue shade demonstrating good light and wash fastness in the range of that realized by dyeingprocesses requiring 1 to 4 hours for the same polymer and dyestulf.

(b) The same spinning dope was extruded by the second procedure set out wherein the coagulation bath is free of dyestufi and a second bath of the same composition containing the dyestufi is positioned immediately after the coagulation bath to treat the aquagel filaments In this case the pick-up of the dye by the filaments in the aquagel state was noticeably less in that a rather light medium blue shade was produced possessing about the same light and wash fastness as the samples in Example VIII (a) above.

Example IX (a) A wet spinning was conducted in the manner of Example VIII (a) above in which the same polymer blend composition was colored by a neutral metallized dye, Cibalan Blue BL. In this case the dye pick-up from the dye-containing coagulation bath by the coagulating filament was excellent and a dark navy blue shade was produced in the resulting filament. The resulting filaments demonstrated an excellent light fastness of at least 80 sunlight fading hours or. more before noticeable shade change, and an acceptable wash fastness when tested by wash test No. 3 at 160 F.

(b) In contrast to IX (a) above 'when the same polymer blend composition was spun into a coagulation bath with a dye-containing second bath the aquag-el filaments picked up virtually no dye at all and were barely stained to an extremely light grey shade in the resulting filaments. Furthermore, these filaments demonstrated a poor light fastness, showing an noticeable break after only 20 sunlight fading hours of exposure in the Fadometer.

Example X (a) A wet spinning by the procedure outlined in Example I was conducted employing a coagulation bath containing 1.5% on the weight of the bath of a dispersed dyestufi, AmacelViolet Blue FSL. This spinning resulted in excellent dye pick-up to a good deep royal blue shade. The knitted samples of the resulting filaments demonstrated good light and wash fastness at least comparable to that realized by dyeing filaments of the same polymer composition with the same dyestuff in the usual 1 to 4 hour dyeing methods.

(b) A wet spinning procedure in which the coagulation bath contains no dyestufi and the immediately adjacent bath of the same composition including the same percent dyestuff as in Example X (a) above was conducted. In this dyeing the aquagel filaments showed notice-ably less pick-up of the dispersed dyestutf and the resulting filaments were a very light pastel shade demonstrating at least 20 sunlight fading hours less fastness to light than the sample from Example X (a) above and somewhat less wiash fastness to wash test No. 3 at 160 F.

(c) A wet spinning procedure the same as that in X (a) Was repeated with the same blended polymer composition and the same dyestuff except that 1.0% of the dyestuff basedon the total weight of coagulation bath was used and the distance of immersion in the bath was shortened to 2 inches from 12 inches to determine the amount of pick-up in the short period of 0.47 second resulting therefrom. It was found that at 1.0% dye based on the total weight of the coagulation bath the pick-up dye by the filament immersed for only 2 inches in the coagulation bath was 2.0% based on the weight of the filament and in the case of that immersed for 12 inches was 2.3% based on the weight of the filament. Therefore, it is seen that the instant process is quite flexible in the length of immersion required, and that in a bath of given concentration may range from 2 inches to as much as 2 to 3 feet with very little change in the total pick-up of dyestuff realized during formation of the fiber. This may be accounted for, at least in part, by the fact that the infusion of dyestuff into the coagulating filament takes place early in its immersion in the coagulating bath.

Example XI A series of wet spinnings was conducted in the manner of the above examples in which the concentration of dye in the coagulation bath was varied from 0.1% to 1.0% based on the weight of the coagulation bath of an acetate dye, A macel Violet Blue PSI. An 18% solids dope of the same polymer as employed in Examples VIII, IX and X above was extruded into a series of coagulation baths containing the varying amounts of dyestuff and the percent dye found in the finished and dried filaments as determined by dissolving the filaments in dimet-hylacetamide solvent and extracting the dye present was determined for each level of dye in the coagulation baths. The results of these determinations are set out in Table 11 beLoW.

TABLE 11 Percent dye in bath: Percent dye in fiber 0.1 0.4 0.2 0.7 0.4 1.4 0.7 2.2 1.0 2.3

it is apparent from the above data that the amount of dye found present in the finished filament can be controlled by varying the amounts of dye in the bath up to an approximate maximum of about. 0.8% dyestutf. A-bov e this amount present in the bath there is no increase in the amount of dye taken up by the fiber irrespective of the concentration of dyestuff present in the coagulation bath. This enables etficient wet: spinning in that a considerable excess of dye can be charged to the coagulation bath initially and an essentially constant amount of dye. will be found in the resulting filaments until the concentration of bath falls below this figure. Therefore, control of the color and shade obtained may be realized through the variation in the dye used, the pH of the bath and the com-position of the polymer being spun. Independent of these variables, however, are the length of the immersion in the coagulating bath and the concentration of dye, above a relatively low saturating concentration. Thus, it is seen that the process of the present invention is quite flexible in the manner in which it can be carried out to still achieve uniformity in color and shade produced.

Example XII In the following example a similar wet spinning was carried out but with variation in the pH maintained in the coagulation bath containing an acid. dye, Calcocid Alizarine Blue SAPX (Acid Blue 45; C.I. 6 3010). In these samples the pH of the coagulation bath was varied to 2.0, 4.0 and 6.0 with 0.5% of the dyestuif present based on the total weight of the coagulation bath. The three spinning samples showed the percent dye pick-up byt-he resulting filaments set out in Table 12 below:

TABLE 12 pH of coagulation bath Percent dye on filament 2.0 3.6 4.0 1.9 6.0 0.3

These results are effective to show two things about the process of the present invention. The best dyeing with the present process is found to lie at the pH at which a specific tdyestufr is most substantive to the specific polymer used. Thus, in this example the acid dye employed was found to be most substantive at a pH of approximate- 1y 2.0 to 2.5, which is the pH at which such dyes are applied normally to the acrylonitrile polymer filament or fiber of this composition. In addition, these results demonstrate that the amount of dye pick-up can be controlled quite readily by variation in the pH of the coagulation bath employed without affecting the ability to coagulate excellent filaments therein. Thus it is shown that the pH of the coagulation bath has very little effect on the coagulation rate of the filaments but has a pronounced effect on the percent of dye pick-up by the forming filaments depending on the type of dyestuff and the pH at which such a dye is most substantive to the poly-mer.

Example XIII In this example a polymer blend composition of a different type than the acrylonitrile copolymers and copolymer blends of the above examples was colored by the process of the present invention. In this example a wet spinning was carried out by the same procedure as in the Examples I through VII above with a polymer blend composed of 85% by weight of a copolymer of 94% acrylonitrile and 6% acetate with by Weight of polyvinyl pyrrolidone blended therewith. The spinning dope was prepared as a solids dope in dimethylacetamide containing 2% by weight of acetic acid. The spinning was carried out in the same way as described in the above examples with 1.5 percent of a neutral metallized dye, Cibalan Blue BL, and otherwise completed as above. The resulting filaments when knitted into test samples demonstrated a surprisingly excellent light fastness of more than 120 sunlight fading hours to first shade change. When the above spinning was repeated employing 1.5% on the total weight of the coagulation bath of another neutral metallized dye, Capracyl RedrB, the resulting knitted samples of finished filament demonstrated a surprising light fastness of 300 sunlight fading hours to first shade change. This example domonstrates that the process of the present invention is suitable for use with many different types of acrylonitrile polymers, copolymers and blends.

When the above coloration and wet spinning examples are repeated with the same dyestuffs but employing spinning dopes of the same or similar acrylonitrile copolymers and blends dissolved in aqueous solutions of metallic salts, such as a 40% solution of calcium chloride and zinc chloride in water, and these spinning dopes are extruded into coagulation baths of more dilute aqueous solutions of the same salts, such as calcium chloride and zinc chloride solutions of 12 to 18% at room temperature or below, the same excellent results in dye pick-up, total coloration, and f-astness to light and washing are obtained. Similar results are realized when spinning dopes of the same polymers in dimethylacetamide solution into coagulating baths of polyethylene glycol with up to 20% dimethylacetamide and aliphatic hydrocarbons with up to 20% dimethylacetamide containing dyestuffs which are soluble or dis-persible in the polyethylene glycol and aliphatic hydrocarbon coagulating baths.

As has been demonstrated in the examples set out above the process of this invention affords many distinct advantages over those coloring processes known in the prior art. The present process affords an extremely rapid and efficient method of coloring acrylonitrile polymer fibers when compared to all the previously known methods. Increases in speed by factors of two to three thousand times have been demonstrated over those usual dyeing processes carried out on the finished filaments or fibers. Furthermore the process of this invention requires, in general, less total expenditure of dyestulf, labor and equipment than previous processes. This process can be carried out on existing production equipment for acrylonitrile polymer filaments and fibers Without the necessity of providing separate additional equipment for the coloring process. In addition, the acrylonitrile polymer filaments and fibers Produced y the pr process demonstrate relatively high fastness to washing and light, at least as good as those demonstrated by the prior art processes and, in many cases, much better. Of even greater importance is the ability through the use of the preesnt process to employ classes and types of dyestuffs previously totally unavailable for the coloration of acrylonitrile polymer filaments and fibers, as has been fully demonstrated above. Because of the presence of all of these advantages the process of the present invention affords great economies in the production of colored acrylonitrile polymer filaments and fibers and produces such products having properties superior to those produced by prior art existing processes.

As many variations within the spirit and scope of this invention will occur to those skilled in the art, it is to be understood that the present invention is not limited to specific embodiments thereof except as set forth in the appended claims.

I claim: I

1. A process for coloring acrylonitrile polymer filaments which consists in extruding a solution of an acrylonitrile polymer comprising at least acrylonitrile and up to 20% of at least one other copolymerizable monoolefinic monomer in a solvent therefor into a coagulation bath consisting of a precipitant for the polymer and from 0.1 to 10% of a dyestuff soluble therein, coagulating colored filaments in said coagulation bath for a period ranging from one-half to ten seconds, and withdrawing the resulting colored coagulated filaments therefrom.

2. The process of claim 1 wherein theacrylonitrile polymer is a copolymer of at least 90% acrylonitrile and up to 10% of vinyl acetate.

3. The process of claim 1 wherein the acrylonitrile polymer is a blend of from 80 to 98% by weight of an acrylonitrile polymer of at least 80% acrylonitrile and up to 20% of another copolymerizable monoolcfinic monomer and from 2 to 20% by weight of a blending polymer of at least 30% of an alkenyl-substituted N-heterocyclic tertiary compound and up to 70% of another copolymerizable monoolefinic monomer.

4. The process of claim 1 wherein the dyestuff is a basic dye.

5. The process of claim 1 wherein the dyestuff is an acid dye.

6. The process of claim 1 wherein the dyestuff is a sulfur dye.

7. The process of claim 1 wherein the dyestuff is a dispersed dye.

8. The process of claim 1 wherein the dyestuff is a neutral metallized dye.

9. The process of claim 1, wherein the acrylonitrile polymer is a blend of 8098% by weight of (a) a polymer of at least 80% acrylonitrile and up to 20% of vinyl acetate and (b) a polymer of at least 30% vinyl pyrrolidone and up to 70% acrylonitrile.

10. A process for coloring acrylonitrile polymer filaments which consists in extruding a solution of an acrylonitrile polymer comprising at least 80% acrylonitrile and up to 20% of at least one other copolymerizable monoolefinic monomer in an organic solvent therefor into a coagulation bath comprising water and from 0.1 to 10% of a dyestutf soluble therein, coagulating colored filaments in said coagulation bath for a period ranging from onehalf to ten seconds, and withdrawing the resulting colored coagulated filaments therefrom.

11. A process for coloring acrylonitrile polymer filaments which consists in extruding a solution of an acrylonitrile polymer comprising at least 80% acrylonitrile and up to 20% of at least one other copolymerizable monoolefinic monomer in an organic solvent therefor selected from the group consisting of dimethylforrnamide and dimethylacetamide into a coagulation bath consisting of water, from 20 to of an organic solvent for said polymer selected from the group consisting of dimethylformamide and dimethylacetamide, and from 0.2 to 3% of a dyestuff soluble therein, coagulating colored filaments References Cited by the Examiner UNITED STATES PATENTS 2,216,793 10/1940 Sowter et al 18-54 2,558,735 7/1951 Cresswell.

1 4 OTHER REFERENCES Review of Textile Progress, 1951, published in England by The Textile Institute and the Society of Dyers and 5 Colourists (copy in Sci. Lib.); page 373 is relied upon.

ALEXANDER H. BRODMERKEL, Primary Examiner. MORRIS LIEBMAN, ROBERT F. WHITE, Examiners. 

1. A PROCESS FOR COLORING ACRYLONITRILE POLYMER FILAMENTS WHICH CONSISTS IN EXTRUDING A SOLUTION OF AN ACRYLONITRILE POLYMER COMPRISING AT LEAST 80% ACRYLONITRILE AND UP TO 20% OF AT LEAST ONE OTHER COPOLYMERIZABLE MONOOLEFINIC MONOMER IN A SOLVENT THEREFOR INTO A COAGULATION BATH CONSISTING OF A PRECIPITANT FOR THE POLYMER AND FROM 0.1 TO 10% OF A DYESTUFF SOLUBLE THEREIN, COAGULATING COLORED FILAMENTS IN SAID COAGULATION BATH FOR A PERIOD RANGING FROM ONE-HALF OF TEN SECONDS, AND WITHDRAWING THE RESULTING COLORED COAGULATED FILAMENTS THEREFROM. 